Power transmitting mechanism



" Patented 1...... 2a, 1932" UNITED STATES PATENT orncs HENRY C. HARRISON, OF PORT WASHINGTON, NEW YORK, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK original application This invention relates to power transmit-- ting mechanism...

The present application is a divison of application, Serial No. 111,707, filed May 26;

An object of this invention is to provide a power transmitting mechanism in which the normal manufacturing inaccuracies in thegears are prevented from affecting theangular constancy of rotation of the load.

A further object of this invention is to provide a ower transmitting mechanism in which vlbration'of the moving parts is to a considerable extent absorbed, and in which the generation and transmission of low frequency vibrations is substantially eliminated.

According to the present invention, I a mechanism for transmitting power with constancy of angular rotation while substantially suppressing the generation or transmission of undesirable vibrations, comprises a multilayer worm gear having its respective layers connected to a shaft by means of springs, said springs being provided with means for damping vibrations therein.

The invention is shown applied as a driving arrangement for a phonograph turntable but is, of course, applicable to a variety of uses.

In this particular application, the problem is to drive a shaft, carrying a phonograph turntable from a driven shaft by means of a gear connection. This gear connection must e of such nature as'to give constancy of angular rotation and to eliminate insofar as possible all mechanical vibration. In thepresent case, the gears used are a worm wheel of unusual construction'd'riven by a worm.

It is well known that, after a gear train has will be worn down till there is an apparent smoothness of operation. In the case of 'aworm-gear train with the wormirunnmg at apparently'uniform peripheral speed .of the worm wheel willbe obtained. However, if there were originally any irregularity in the gears, as there usually will be in spite of care- .ful manufacture, then this constant periphbeen run fora time, irregularities in the gears" constant sped afterthe gears are runin, an

eral speed will not give a constant angular- .rownnmnaivsmir'rme mncrmlvism filed May 26, 1926, Serial No. 111,707, and in Germany December 18, 1926. Divided. and this application tiled January 28, 1929. Serial No. 335,609.

rotation since the constant peripheral speed is being applied to a surface having a varying radius of curvature. I

Having broadly outlined above some of the general features of the invention, a better understanding of a typical embodiment will be'had from the following detailed description in connection with the accompanying drawing. Referring to the drawing:

Fig. 1 shows an elevation of the mechanism partly in section.

Fig. 2 shows a fluid damping device.

Fig. 3 shows the worm gear train connecting the driving and driven shafts.

Fig. 4 is a view, partly in section, of the multi-layer wormgear and the spring conmotion to the driven shaft.

The mechanism is supported by a casting 150 which in turn is supported by a suitable pedestal or base (not shown). A turntable 151 upon which a record 21 may be placed is mounted on the vertical shaft 152. The

lower layer 110 of the worm gear is a simple ring and is concentrically supported by a bearlng in the lower end of the housing 154.

The upper layer 111 of the gear bears on the upper surface of the layer 110 and is integral with a. cup-shaped member which holds layer- 110 in operative relation with layer 111 and retains the gear-as a whole against lateral movement. A collar '157 is secured to the up-.

per layer 111 of. the worm gear to prevent longitudinal movement of the gear and is provided with a bearing surface against the bottom of the housing 154, and a washer 158 of suitable material to prevent any appreciable leakage of lubricant from the housing 154. The collar 157 may be formed as a pulley symmetrically positioned with respect to for and used as a belt pulley to supply power not 7 {)ustably attached to the upper member 159 y means of bolts 161. These two members are thus held together and to the collar 157 so that they all rotate in unison with the worm gear.

The vertical shaft 152 which supports the turntable 151, is provided at its lower end with a member 162 comprising a device carrying a number ofradial vanes which fit closely within the lower member 160 of-the damping device, but are not attached thereto. Member 160 is provided with a number of internal radial vanes as is clearly shown in Fig. 2. Preferably these members will have equal numbers of vanes and as shown in the present embodiment, there are four vanes on the member 162 and four vanes on the member 160. The radial vanes of each member are symmetrically located and are each other, and so machined as to allow a small clearance.- The chamber formed by members'159 and 160 is filled with some suitable fluid such as oilto above the top of mem ber 162. When a small angular displacement takes place between members '160 and 162, the fluid is forced through the clearance .passages from. one section to another between the vanes and thus the desired damping is ob tained. By lowering or raising the member 160 the clearance between the vanes and the case is increased or decreased thus varying the damping till the desired effect is obtained.

By this arrangement, the damping device frictional drag on the shaft 152.

laces no i t'hen the angular, speed of the worm gear 1s crease 111 constant, the damplng device is entirely inactiveybut 'i'ipon'any sudden increase ,or derotation, the damping device immediately becomes efiective. v

In Figs. 3 and 4 are shown side and edge views, partly in section, of the novel multilayer worm gear. This worm gear has been devised'to compensate for the irregularitiesinherent in a worm gear of commercial manufacture and thereby approach the action of a perfectly formed worm gear. Its design is such that the amplitude of the angular speed variation is decreased and the frequency of the vibrations set up during operation is increased. By decreasing the amplitude and increasing the frequency of such disturbances they may be more readily eliminated by filtering methods such as are described in the parent specification.

The worm gear consists of two or more thin discs or layers which are clamped together and cut simultaneously in the usual manner. The layers are then reassembled in an angular relation other than that occupied during the cutting operation. The variations in out have been found to be cyclic and the best practical displacement of each layer is a progressive displacement equal'to 360 divided by the number of layers. Thus, if two layers are used to make up the gear, after cutting the layers will be placed so that corresponding points will be 180 apart. If three layers are used, the spacing of the originally corresponding points will be 120 apart between successive layers, while if four layers are used the layers are shifted 90 apart. Thus the high spots of one layer will be more or less in alignment with low spots on the other layers thus producing a composite gear which on the average will operate more nearly perfectly than a single piece worm gear of normal accuracy of manufacture.

The superimposed layers are free to rotate slightly with regard to each other and are individually and elastically coupled to the driven shaft. The composite gear is driven as a whole by a common worm. The action of this multi-layer worm gear is to average out the angular errors in the driving faces of the layers and also to reduce any ing action on the threads of the worm.

' The worm gear shown is made up of two layers 110 and 111. The lower layer 110 of the gear has secured thereto two pins 112 and 115 passing through slots 118 and 119 in the upper layer 111. These slots will allow a relative angular movement of the layers. The upper end 0t pin 112 is connected to springs 113 and 114; theupper end of pin 115 is connected to springs 116 and 117; the free ends of the springs are connected to a starshaped member 127 which is rigidly secured to theshaft 152. Similarly the upper layer 111 of the gear carries two pins 120 and 123 which are connected by means of springs 121, 122, 124 and 125 to astar-shaped member 128 rigidly secured to the shaft 152.' To provide damping for the spring elasticities, a wrapping 129 of felt or similar material enclosed by a slitted thin elastic tube may be employed. The slitted tube prevents the felt from stretching with the spring and holds the damping material in position. The use of damping with helical springs makes possible the use of very light springs with a corresponding gain in the efiioiency of suppression of vibrations.

It is obvious that this gear arrangement not only provides an elastic coupling between the driving shaft 129 and the driven shaft 152, but that by displacing the layers after cutting any irregularities are averaged so as to produce a rotation of the driven shaft which is more uniform than would otherwise be obtained unless the gears were perfectly cut. The relative angular movement between the layers, with the individual yielding connection to the driven shaft allows irregularities to adjust themselves when passing the worm much more smoothly than would otherwise be possible. The combination of-the fluid damping means on the shaft, the damping on the springs and the relative freedom of the shaft due to the elastic connection will largely prevent the generation or transmission ofvibrations.

What-is claimed is:

1. A gear wheel comprising a plurality of coaxial discs progressively and equally displaced around the circumference of the gear from the positions assumed during the cutting of the gear.

2. A gear wheel comprising a plurality of superimposed coaxial discs equiangularly displaced from the positions assumed during cutting. and individually and resiliently connected to the driven shaft.

In witness whereof, I hereunto subscribe my name this 25th day of January, 1929,

HENRY G. HARRISON. 

